task IO accounting: improve code readability

Put all i/o statistics in struct proc_io_accounting and use inline functions to
initialize and increment statistics, removing a lot of single variable
assignments.

This also reduces the kernel size as following (with CONFIG_TASK_XACCT=y and
CONFIG_TASK_IO_ACCOUNTING=y).

    text    data     bss     dec     hex filename
   11651       0       0   11651    2d83 kernel/exit.o.before
   11619       0       0   11619    2d63 kernel/exit.o.after
   10886     132     136   11154    2b92 kernel/fork.o.before
   10758     132     136   11026    2b12 kernel/fork.o.after

 3082029  807968 4818600 8708597  84e1f5 vmlinux.o.before
 3081869  807968 4818600 8708437  84e155 vmlinux.o.after

Signed-off-by: Andrea Righi <righi.andrea@gmail.com>
Acked-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

7 files changed, 104 insertions, 114 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index e74308bdabd3..3d94906c7aa8 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -53,6 +53,7 @@
 #include <linux/time.h>
 #include <linux/proc_fs.h>
 #include <linux/stat.h>
+#include <linux/task_io_accounting_ops.h>
 #include <linux/init.h>
 #include <linux/capability.h>
 #include <linux/file.h>
@@ -2402,44 +2403,17 @@ static int proc_base_fill_cache(struct file *filp, void *dirent,
 #ifdef CONFIG_TASK_IO_ACCOUNTING
 static int do_io_accounting(struct task_struct *task, char *buffer, int whole)
 {
-        u64 rchar, wchar, syscr, syscw;
-        struct task_io_accounting ioac;
-
-        rchar = task->rchar;
-        wchar = task->wchar;
-        syscr = task->syscr;
-        syscw = task->syscw;
-        memcpy(&ioac, &task->ioac, sizeof(ioac));
-
-        if (whole) {
-                unsigned long flags;
-
-                if (lock_task_sighand(task, &flags)) {
-                        struct signal_struct *sig = task->signal;
-                        struct task_struct *t = task;
-
-                        rchar += sig->rchar;
-                        wchar += sig->wchar;
-                        syscr += sig->syscr;
-                        syscw += sig->syscw;
-
-                        ioac.read_bytes += sig->ioac.read_bytes;
-                        ioac.write_bytes += sig->ioac.write_bytes;
-                        ioac.cancelled_write_bytes +=
-                                        sig->ioac.cancelled_write_bytes;
-                        while_each_thread(task, t) {
-                                rchar += t->rchar;
-                                wchar += t->wchar;
-                                syscr += t->syscr;
-                                syscw += t->syscw;
-
-                                ioac.read_bytes += t->ioac.read_bytes;
-                                ioac.write_bytes += t->ioac.write_bytes;
-                                ioac.cancelled_write_bytes +=
-                                        t->ioac.cancelled_write_bytes;
-                        }
-                        unlock_task_sighand(task, &flags);
-                }
+        struct proc_io_accounting acct = task->ioac;
+        unsigned long flags;
+
+        if (whole && lock_task_sighand(task, &flags)) {
+                struct task_struct *t = task;
+
+                task_io_accounting_add(&acct, &task->signal->ioac);
+                while_each_thread(task, t)
+                        task_io_accounting_add(&acct, &t->ioac);
+
+                unlock_task_sighand(task, &flags);
         }
         return sprintf(buffer,
                         "rchar: %llu\n"
@@ -2449,9 +2423,10 @@ static int do_io_accounting(struct task_struct *task, char *buffer, int whole)
                         "read_bytes: %llu\n"
                         "write_bytes: %llu\n"
                         "cancelled_write_bytes: %llu\n",
-                        rchar, wchar, syscr, syscw,
-                        ioac.read_bytes, ioac.write_bytes,
-                        ioac.cancelled_write_bytes);
+                        acct.chr.rchar, acct.chr.wchar,
+                        acct.chr.syscr, acct.chr.syscw,
+                        acct.blk.read_bytes, acct.blk.write_bytes,
+                        acct.blk.cancelled_write_bytes);
 }
 
 static int proc_tid_io_accounting(struct task_struct *task, char *buffer)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f59318a0099b..034c1ca6b332 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -505,10 +505,7 @@ struct signal_struct {
         unsigned long nvcsw, nivcsw, cnvcsw, cnivcsw;
         unsigned long min_flt, maj_flt, cmin_flt, cmaj_flt;
         unsigned long inblock, oublock, cinblock, coublock;
-#ifdef CONFIG_TASK_XACCT
-        u64 rchar, wchar, syscr, syscw;
-#endif
-        struct task_io_accounting ioac;
+        struct proc_io_accounting ioac;
 
         /*
          * Cumulative ns of scheduled CPU time for dead threads in the
@@ -1256,11 +1253,7 @@ struct task_struct {
 
         unsigned long ptrace_message;
         siginfo_t *last_siginfo; /* For ptrace use.  */
-#ifdef CONFIG_TASK_XACCT
-/* i/o counters(bytes read/written, #syscalls */
-        u64 rchar, wchar, syscr, syscw;
-#endif
-        struct task_io_accounting ioac;
+        struct proc_io_accounting ioac;
 #if defined(CONFIG_TASK_XACCT)
         u64 acct_rss_mem1;      /* accumulated rss usage */
         u64 acct_vm_mem1;       /* accumulated virtual memory usage */
@@ -2190,22 +2183,22 @@ extern long sched_group_rt_period(struct task_group *tg);
 #ifdef CONFIG_TASK_XACCT
 static inline void add_rchar(struct task_struct *tsk, ssize_t amt)
 {
-        tsk->rchar += amt;
+        tsk->ioac.chr.rchar += amt;
 }
 
 static inline void add_wchar(struct task_struct *tsk, ssize_t amt)
 {
-        tsk->wchar += amt;
+        tsk->ioac.chr.wchar += amt;
 }
 
 static inline void inc_syscr(struct task_struct *tsk)
 {
-        tsk->syscr++;
+        tsk->ioac.chr.syscr++;
 }
 
 static inline void inc_syscw(struct task_struct *tsk)
 {
-        tsk->syscw++;
+        tsk->ioac.chr.syscw++;
 }
 #else
 static inline void add_rchar(struct task_struct *tsk, ssize_t amt)
diff --git a/include/linux/task_io_accounting.h b/include/linux/task_io_accounting.h
index 44d00e9cceea..165390f8b936 100644
--- a/include/linux/task_io_accounting.h
+++ b/include/linux/task_io_accounting.h
@@ -1,5 +1,5 @@
 /*
- * task_io_accounting: a structure which is used for recording a single task's
+ * proc_io_accounting: a structure which is used for recording a single task's
  * IO statistics.
  *
  * Don't include this header file directly - it is designed to be dragged in via
@@ -8,6 +8,22 @@
  * Blame akpm@osdl.org for all this.
  */
 
+#ifdef CONFIG_TASK_XACCT
+struct task_chr_io_accounting {
+        /* bytes read */
+        u64 rchar;
+        /*  bytes written */
+        u64 wchar;
+        /* # of read syscalls */
+        u64 syscr;
+        /* # of write syscalls */
+        u64 syscw;
+};
+#else /* CONFIG_TASK_XACCT */
+struct task_chr_io_accounting {
+};
+#endif /* CONFIG_TASK_XACCT */
+
 #ifdef CONFIG_TASK_IO_ACCOUNTING
 struct task_io_accounting {
         /*
@@ -31,7 +47,12 @@ struct task_io_accounting {
          */
         u64 cancelled_write_bytes;
 };
-#else
+#else /* CONFIG_TASK_IO_ACCOUNTING */
 struct task_io_accounting {
 };
-#endif
+#endif /* CONFIG_TASK_IO_ACCOUNTING */
+
+struct proc_io_accounting {
+        struct task_chr_io_accounting chr;
+        struct task_io_accounting blk;
+};
diff --git a/include/linux/task_io_accounting_ops.h b/include/linux/task_io_accounting_ops.h
index ff46c6fad79d..e6f958ebe97f 100644
--- a/include/linux/task_io_accounting_ops.h
+++ b/include/linux/task_io_accounting_ops.h
@@ -9,7 +9,7 @@
 #ifdef CONFIG_TASK_IO_ACCOUNTING
 static inline void task_io_account_read(size_t bytes)
 {
-        current->ioac.read_bytes += bytes;
+        current->ioac.blk.read_bytes += bytes;
 }
 
 /*
@@ -18,12 +18,12 @@ static inline void task_io_account_read(size_t bytes)
  */
 static inline unsigned long task_io_get_inblock(const struct task_struct *p)
 {
-        return p->ioac.read_bytes >> 9;
+        return p->ioac.blk.read_bytes >> 9;
 }
 
 static inline void task_io_account_write(size_t bytes)
 {
-        current->ioac.write_bytes += bytes;
+        current->ioac.blk.write_bytes += bytes;
 }
 
 /*
@@ -32,17 +32,25 @@ static inline void task_io_account_write(size_t bytes)
  */
 static inline unsigned long task_io_get_oublock(const struct task_struct *p)
 {
-        return p->ioac.write_bytes >> 9;
+        return p->ioac.blk.write_bytes >> 9;
 }
 
 static inline void task_io_account_cancelled_write(size_t bytes)
 {
-        current->ioac.cancelled_write_bytes += bytes;
+        current->ioac.blk.cancelled_write_bytes += bytes;
 }
 
-static inline void task_io_accounting_init(struct task_struct *tsk)
+static inline void task_io_accounting_init(struct proc_io_accounting *ioac)
 {
-        memset(&tsk->ioac, 0, sizeof(tsk->ioac));
+        memset(ioac, 0, sizeof(*ioac));
+}
+
+static inline void task_blk_io_accounting_add(struct proc_io_accounting *dst,
+                                                struct proc_io_accounting *src)
+{
+        dst->blk.read_bytes += src->blk.read_bytes;
+        dst->blk.write_bytes += src->blk.write_bytes;
+        dst->blk.cancelled_write_bytes += src->blk.cancelled_write_bytes;
 }
 
 #else
@@ -69,9 +77,37 @@ static inline void task_io_account_cancelled_write(size_t bytes)
 {
 }
 
-static inline void task_io_accounting_init(struct task_struct *tsk)
+static inline void task_io_accounting_init(struct proc_io_accounting *ioac)
+{
+}
+
+static inline void task_blk_io_accounting_add(struct proc_io_accounting *dst,
+                                                struct proc_io_accounting *src)
 {
 }
 
-#endif          /* CONFIG_TASK_IO_ACCOUNTING */
-#endif          /* __TASK_IO_ACCOUNTING_OPS_INCLUDED */
+#endif /* CONFIG_TASK_IO_ACCOUNTING */
+
+#ifdef CONFIG_TASK_XACCT
+static inline void task_chr_io_accounting_add(struct proc_io_accounting *dst,
+                                                struct proc_io_accounting *src)
+{
+        dst->chr.rchar += src->chr.rchar;
+        dst->chr.wchar += src->chr.wchar;
+        dst->chr.syscr += src->chr.syscr;
+        dst->chr.syscw += src->chr.syscw;
+}
+#else
+static inline void task_chr_io_accounting_add(struct proc_io_accounting *dst,
+                                                struct proc_io_accounting *src)
+{
+}
+#endif /* CONFIG_TASK_XACCT */
+
+static inline void task_io_accounting_add(struct proc_io_accounting *dst,
+                                                struct proc_io_accounting *src)
+{
+        task_chr_io_accounting_add(dst, src);
+        task_blk_io_accounting_add(dst, src);
+}
+#endif /* __TASK_IO_ACCOUNTING_OPS_INCLUDED */
diff --git a/kernel/exit.c b/kernel/exit.c
index 0caf590548a0..eb4d6470d1d0 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -121,18 +121,7 @@ static void __exit_signal(struct task_struct *tsk)
                 sig->nivcsw += tsk->nivcsw;
                 sig->inblock += task_io_get_inblock(tsk);
                 sig->oublock += task_io_get_oublock(tsk);
-#ifdef CONFIG_TASK_XACCT
-                sig->rchar += tsk->rchar;
-                sig->wchar += tsk->wchar;
-                sig->syscr += tsk->syscr;
-                sig->syscw += tsk->syscw;
-#endif /* CONFIG_TASK_XACCT */
-#ifdef CONFIG_TASK_IO_ACCOUNTING
-                sig->ioac.read_bytes += tsk->ioac.read_bytes;
-                sig->ioac.write_bytes += tsk->ioac.write_bytes;
-                sig->ioac.cancelled_write_bytes +=
-                                        tsk->ioac.cancelled_write_bytes;
-#endif /* CONFIG_TASK_IO_ACCOUNTING */
+                task_io_accounting_add(&sig->ioac, &tsk->ioac);
                 sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
                 sig = NULL; /* Marker for below. */
         }
@@ -1363,21 +1352,8 @@ static int wait_task_zombie(struct task_struct *p, int options,
                 psig->coublock +=
                         task_io_get_oublock(p) +
                         sig->oublock + sig->coublock;
-#ifdef CONFIG_TASK_XACCT
-                psig->rchar += p->rchar + sig->rchar;
-                psig->wchar += p->wchar + sig->wchar;
-                psig->syscr += p->syscr + sig->syscr;
-                psig->syscw += p->syscw + sig->syscw;
-#endif /* CONFIG_TASK_XACCT */
-#ifdef CONFIG_TASK_IO_ACCOUNTING
-                psig->ioac.read_bytes +=
-                        p->ioac.read_bytes + sig->ioac.read_bytes;
-                psig->ioac.write_bytes +=
-                        p->ioac.write_bytes + sig->ioac.write_bytes;
-                psig->ioac.cancelled_write_bytes +=
-                                p->ioac.cancelled_write_bytes +
-                                sig->ioac.cancelled_write_bytes;
-#endif /* CONFIG_TASK_IO_ACCOUNTING */
+                task_io_accounting_add(&psig->ioac, &p->ioac);
+                task_io_accounting_add(&psig->ioac, &sig->ioac);
                 spin_unlock_irq(&p->parent->sighand->siglock);
         }
 
diff --git a/kernel/fork.c b/kernel/fork.c
index 5e050c1317c4..8214ba7c8bb1 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -806,12 +806,7 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
-#ifdef CONFIG_TASK_XACCT
-        sig->rchar = sig->wchar = sig->syscr = sig->syscw = 0;
-#endif
-#ifdef CONFIG_TASK_IO_ACCOUNTING
-        memset(&sig->ioac, 0, sizeof(sig->ioac));
-#endif
+        task_io_accounting_init(&sig->ioac);
         sig->sum_sched_runtime = 0;
         INIT_LIST_HEAD(&sig->cpu_timers[0]);
         INIT_LIST_HEAD(&sig->cpu_timers[1]);
@@ -994,13 +989,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         p->last_switch_timestamp = 0;
 #endif
 
-#ifdef CONFIG_TASK_XACCT
-        p->rchar = 0;           /* I/O counter: bytes read */
-        p->wchar = 0;           /* I/O counter: bytes written */
-        p->syscr = 0;           /* I/O counter: read syscalls */
-        p->syscw = 0;           /* I/O counter: write syscalls */
-#endif
-        task_io_accounting_init(p);
+        task_io_accounting_init(&p->ioac);
         acct_clear_integrals(p);
 
         p->it_virt_expires = cputime_zero;
diff --git a/kernel/tsacct.c b/kernel/tsacct.c
index 3da47ccdc5e5..f9cd2561689c 100644
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -94,14 +94,14 @@ void xacct_add_tsk(struct taskstats *stats, struct task_struct *p)
                 stats->hiwater_vm    = mm->hiwater_vm * PAGE_SIZE / KB;
                 mmput(mm);
         }
-        stats->read_char        = p->rchar;
-        stats->write_char       = p->wchar;
-        stats->read_syscalls    = p->syscr;
-        stats->write_syscalls   = p->syscw;
+        stats->read_char        = p->ioac.chr.rchar;
+        stats->write_char       = p->ioac.chr.wchar;
+        stats->read_syscalls    = p->ioac.chr.syscr;
+        stats->write_syscalls   = p->ioac.chr.syscw;
 #ifdef CONFIG_TASK_IO_ACCOUNTING
-        stats->read_bytes       = p->ioac.read_bytes;
-        stats->write_bytes      = p->ioac.write_bytes;
-        stats->cancelled_write_bytes = p->ioac.cancelled_write_bytes;
+        stats->read_bytes       = p->ioac.blk.read_bytes;
+        stats->write_bytes      = p->ioac.blk.write_bytes;
+        stats->cancelled_write_bytes = p->ioac.blk.cancelled_write_bytes;
 #else
         stats->read_bytes       = 0;
         stats->write_bytes      = 0;